Like lots of people, I never thought I'd be a teacher when I was at school. To be honest, I only did my training because my husband was on a four-year course and I was on a three-year course at Cardiff University, so I wanted to do something for one year. I thought doing a teaching qualification would be interesting and might be quite useful.

My first teaching practice, as part of the course, was in a primary school for three weeks. Although it was fun, the kids were running wild. I didn't feel I could control them and I thought: "this is hopeless - I just can't do this".

But when I went into a secondary classroom, to teach my own subject, it was a completely different experience. Passing on a love of literature was wonderful, and I realised that I could never be bored teaching with so much variety in the job. Teaching itself is never boring - the kids are so entertaining, they always surprise you.

I'm convinced that nothing else I might have done would have given me so much pleasure and satisfaction, or fitted in so well with family life.

When I retire, in just a few years time, I can look back on a career which made a positive difference to the lives of thousands of children. Few other career choices can be so rewarding; so if you have a love of your subject, and want the opportunity to pass that on, then teaching can be a great career.

It was completely different then, of course. I trained 30 years ago and in the first 20 years of my career I was observed just once – and that includes my probation year. In those days the classroom was your kingdom. There really was very little direction and no such thing as a formulaic approach. You were left to your own devices to sink or swim.

Now, there's so much more direction from outside and there's good and bad in that. It's created more standardisation; certainly teachers who aren't putting effort in will be forced out.

Anyone going into teaching now will be used to teaching to formal work schemes and observation. I think it has raised standards in the profession but, personally, I feel the loss in the classroom. I've got the confidence of 30 years experience. I've seen new approaches come and go; sometimes even identical 'new ideas' come and go more than once.

For me, it's the passion for your subject and interest in the success of your students that matters more than how all the acronyms add up. This is what will make you a good teacher. There's still room for individuals but you have to have the confidence and passion for your subject to make it work.

The major challenge in teaching is time; there's not enough of it. It's hard if you're working full time to cope with the marking and feel like you have enough time to do your job properly. I've worked part time ever since I had children. I officially work three days a week, but on my two days off I always work. It probably all adds up to what counts as a full-week's work in most other jobs but the pay isn't bad, so you can work part time and then the job really does fit in with family life. There are shortcuts to save time and if I had to work full time I'd have to use them. But working part time gives me the luxury to be a fussy marker. It can take two hours to mark a 3,000 word A-level essay, so if you have 16 pupils that's 32 hours of marking in one week for just one class. One of the benefits of being a part-time teacher is that I do have time to mark properly. Sometimes my feedback is almost as long as their essay but I really want the kids to do well.

One of the best things about teaching is you get to raise children's aspirations and make a difference in their lives. You get visits and emails from your old students to prove it. It's great to make the difference and, as they say, it does make it all worthwhile.

The core of teaching is the subject and the pupils. We have a lot of NQTs and PGCE students coming to our school and sometimes I must admit to being disappointed when students don't know their subjects that well. I had an NQT who was teaching Animal Farm who asked me "What's Marxism?" She'd got a first in her degree, so it just goes to show that government initiatives to try and attract those with firsts aren't necessarily going work.

After teaching for 20 years in one school, I've got a reputation. I think I'm known for having high expectations and high standards and pushing my students. Of course some like being pushed and some don't, so there are always challenges.

But generally - when I'm teaching poetry, for example - I'll get kids moaning in the beginning but, a high percentage of the time, when we've finished they'll have found some stuff they like and connect to. That is just as rewarding for me as great A-level results. I can't bear to think that any child will go through their lives not knowing how great literature can affect them, that they can see the world through someone's eyes. They might be living in Chelmsford but they can learn what it's like being an immigrant moving to London through reading a book. Reading for pleasure is such a wonderful thing.

Lots of people drop out of teaching after a couple of years, it is an exhausting job. So my advice to those just starting out is:

• Don't lose your sense of proportion over things that happen in the classroom or in an observation that doesn't go well. As long as in the bigger picture of things you are connecting with kids and the subject, don't get disheartened. Even after 30 years of teaching everyone has appalling days when you think: "Can I really do this?" You've got to keep positive, it's only a problem if you get more bad days than good days.

• Make sure teaching doesn't overwhelm you. You have to develop strategies especially if you are teaching a subject which requires a lot of marking. So plan things well. Get your pupils to do peer marking, which really can work. If you know you just can't handle any more marking in a particular week, get pupils to write a speech and then perform it in the next class. You've got to think ahead about times of maximum workload and plan accordingly - ask your more experienced colleagues for advice.

• You've got to keep your sense of humour; it's a great way of defusing a situation. I know I became a better teacher when I became a parent. I realised that kids can be so obnoxious sometimes, even your own kids. They don't mean it, they're just being kids. It doesn't mean they hate you or hate your lessons. When you're a new teacher coming into teaching, especially if you are young, you think of the students as almost your adversaries, you've got to defeat them. But you've got to be careful what you say. You can't belittle them too much or you can really harm them.

• Love your subject. If you are going to succeed in secondary school teaching you must love your subject, the kids really know if you do or don't.

• You have to know your students are individuals, they learn in different ways, you have to be sensitive to that.

• You can't just teach to a formula. I do worry about the divergence between lip service to what the government say it's supposed to be like and what it's really like. I do hate the hypocrisy of that, and the gulf seems to widen more and more. It feels like what matters most is what's tested. The trouble is, nothing that is really worthwhile can be tested. So the love of learning, connection with literature, having empathy – these are the things that really make a difference to someone's life but of course they can't be tested. Young teachers have to be careful not to get lost in formulas and initiatives. A more experienced teacher will have confidence to respond to kids and to talk about an issue that's raised in class that's not on the plan. The children will learn so much from that but there's no box to tick.

Julia Frascona teaches English at The Boswell's School in Chelmsford where she is also joint head of the library.

Interview by Emily Drabble. If you have an inspiring story to tell and would like to be featured in this page please get in touch with emily.drabble@guardian.co.uk.